Drawing proper refers to the cupping of a blank, as in cutting and cupping processes, or in taking any piece of sheet metal in the form of a blank, and producing therefrom any cup-like shape during which process a flowing of the metal takes place.

The term re-drawing applies to any subsequent drawing processes that follow the first drawing or cupping process as would occur in the manufacture of a cartridge shell or similar work. For instance, if any blank be cupped it may be said to have been drawn or had its first drawing. But if this same cup be further reduced in diameter by being passed through a second pair of tools, then the process of so reducing it will be called re-drawing.

Fig. 135.

Referring to fig. 135, we have two blanks and their respective cups, No. 1 and No. 2. The first, or No. 1 blank, is 1 15/64 in. diameter, and cut from metal .111 in. thick, it has been cupped by a cupping punch .629 in. diameter, and a die bored out to .818 in. in the hole, the thickness of metal has been reduced from .111 in. to .0945 in. during the cupping process. There has, therefore, been .0165 in. draw-on the metal by means of the cupping tools. In the case of No. 2 the blank is •113 in. thick, it has passed through a die having a hole .878 in. diameter, the drawing punch being •680 in. diameter, there has been 014 in. draw on the metal. Had the punch been 652 in. diameter, the blank would have merely passed through the die, coming from the tools in the form of a cup without any draw or flow of the metal taking place. From this it will be readily understood that in any case of drawing an article each process must be considered separately. The thickness of the metal blank and the outside diameter required for the cup are the two points that decide the diameter of the hole in the die. Then twice the thickness of metal blank subtracted from the hole in the die will give the diameter of the cupping punch, if no draw or flow of metal is required. But should it be required to reduce the thickness of metal during the cupping process, then twice the required reduction of the metal thickness must be added to the diameter of the punch. In cases where the size of the hole in the cup is the more important.

Fig 136.

Then the order of things will be reversed, the drawing being arranged by the diameter of the hole in the die-the larger the hole the less the draw, and the smaller the hole the more will be the amount of draw on the metal. A blank and its cup is seen at fig. 136; it will be noticed that the bottom of this cup has a rather sharp corner; this is a point that is governed to a large extent by the shape of the punch. If a sharp corner is required on a cup the end of the drawing punch should be finished by having a small radius on its corner, whereas-if the radius on the corner at the end of the drawing punch be made comparatively larger then the corner of the closed end of the drawn cup-will necessarily have a larger radius. In conical drawing the taper punch forces the blank into a taper die, after which the conical cup will be extracted or lifted from the die, either by the operator's hands or some form of extracting mechanism. The drawing of conical work may in a sense be called raising, in fact, it is at times very difficult to distinguish drawing from raising, because amongst the great varieties of metal work one blank may be stamped or raised in a stamp, whilst another article exactly the same shape may be raised in a power press, the article passing in and out of the die -not through the die-yet a certain amount of flowing may have taken place in the metal whilst the article was being formed into shape, which would probably warrant the term drawing being applied to the process.

Fig. 137 was made in combination tools, the blank being cut out, then held by the cutting-out punch under pressure, whilst the drawing punch (which may in this case be called a raising punch) comes down and draws or raises the blank into the shape, the article being afterwards pushed up and out of the die by an extractor. A somewhat similar example to fig. 137, but of smaller size, is shown at fig. 138. No particular rules with regard to re-drawing processes can be given, since the amount of draw or flow of metal required depends so much upon the nature of the work that is being done. A few examples, however, will enable the student to follow what actually takes place during the different stages of re-drawing. Fig. 139 gives the complete

10wp processes for drawing a German silver shell or case for a cartridge, particulars of which will be found in Table 1., beginning with the blank, and finishing by cutting down or trimming the shell. The small metal sphere, fig. 140, is made in four processes, including the blank cutting. The

Fig. 137.

Fig. 138.